i'd have to say return to castle wolfenstein, halo 3, modern warfare 1 (pc)

ninjaedit: not praising these as the pinnacle of fps, but they had a much clearer correlation of aiming skill and k/d ratio.

All things considered.......Medal of Honor (2010) was actually a very nice FPS.  Smooth as silk (even on low-end machines) and really promoted team-play after they nerfed the sniper gheyness!

Of course the devs (EA and DICE) dropping active support for the game only a month after releasing PAID-for DLC does seem like a swift slap in the face to their community and allowed the game to fall victim to the hacker crowd.  Sad really.....